A broadcast network - all frames that cross a segment can be heard by all
machines on the segment

All machines have equal access, they wait for a quiet time to transmit,
collisions occur when two machines transmit at the same time. When a
collision occurs both the machines apply a back off time that prevents them
from colliding again

Services both the Physical and Data Link layers

Ethernet frame (read right to left)

FSC

Data

Type

Source

Destination

SOF

Preamble

Frame Check Sequence

Data to be handed to the upper layer protocol

Defines which upper layer protocol will receive
the packet

MAC Address

MAC Address

Start of Frame

Beginning of the frame

4 bytes

46-1500 bytes

2 bytes

6 bytes

6 bytes

1 byte

7 bytes

IEEE 802.3

Also a broadcast network

More concerned with the Physical Layer and how it talks to the Data Link
Layer

802.3 frame (read right to left)

FSC

Data

Length

Source

Destination

SOF

Preamble

Frame Check Sequence

Contains 802.2 header and the encapsulated data
to be passed to an upper layer protocol that is defined in data field

Defines how many bytes the 802.2 header and data
field is

MAC Address

MAC Address

Used to synchronize the frame reception portions
of all the machines on the segment

Equal time is allotted to each station. achieved by passing a token around
the ring

Tokens

A small frame, a station cannot transmit data unless in possession of the
token

The Token is passed around the ring, each station waits for the token, if
the station doesn't have anything to transmit, it passes the token
along. If it does have something to transmit, it change the frame to a
start of frame identifier and appends data to the frame. When the
token is changed, no other station on the ring can use the token to transmit
data. This eliminates collisions. The altered frame is passed along
the ring until it reaches the destination address. The destination
station copies the data and the original frame continues around the token
until it reaches the source station. At the source, the token is
removed and a new token is sent out onto the network. This way each
station has an equal opportunity to transmit data.

Fault Recovery - an Active Monitor is designated by the workstations on
the ring